FIELD OF THE INVENTION
The present invention relates generally to a supporting structure of electrostatic precipitator in thermal power plants. More particularly, the invention relates to an improved supporting device converting existing Electrostatic precipitators complaint to statutory level of reduced emission of dust particles.
BACKGROUND OF THE INVENTION
Electrostatic precipitator (ESP) is an equipment in a Thermal Power Plant which extracts the ash existing with the flue gas which is the product of burning pulverized coal in a boiler in the thermal power plant (TPP).
The Electrostatic precipitator uses an electrical phenomenon called "Corona" discharge which under high voltage turns the flue gas into an ionized state where the negatively charged ash particles are attracted towards a positive electrodes called the collecting electrodes which is rapped at intervals by a rapping hammer and collected in ash hoppers disposed at the bottom of the electrostatic precipitators.
The weight of the collected ash and the weight of the collecting electrodes constitute the major vertical loads sustained by the foundations of the supporting structure of the electrostatic precipitators, apart from the wind and seismic loads.

The electrostatic precipitators are designed for a particular value of permissible emission levels i.e. the amount of dust particles present in the flue gas that is let out into the atmosphere through the chimney. These emission levels are normally fixed by the Statutory Authorities.
These permitted value of emission levels are being reduced to a more stringent value periodically over the decades by the statutory authorities.
The currently permitted emission levels call for a modification of the already installed electrostatic precipitators, initially designed for a higher emission levels, to bring down the emission levels to the lower current norms. A straight forward solution to this problem is to replace the existing electrostatic precipitators with higher capacity ESP to satisfy the lower current emission norms. The modification of the ESP is likely to increase the vertical load on the foundations of the electrostatic precipitator as both the amount of collected ash and the size of collecting electrodes are destined to increase considerably.
This process of replacing the existing electrostatic precipitator with new bigger electrostatic precipitators in the same location of the TPP i.e. between the boiler and induced draft fan is called Retrofitting of the electrostatic precipitators.
The Electrostatic precipitator is basically a rectangular box which houses a plurality of collecting electrodes and emitting electrodes which separates the ash from the flue gas passing through the ESP. Hoppers are provided underneath the rectangular box to temporarily store the collected ash. The shape of the hopper is an inverted pyramid. The rectangular box and the pyramidal hopper are supported by steel columns fabricated out of Rolled steel Beams or Channels.

The supporting structure of the Electrostatic precipitator takes care of the loads exerted on it by the weight of the collecting electrodes and the collected ash in the hoppers. The hoppers are generally designed for the storage of ash collected in eight hours of operation of the ESP. The ash collected in the hoppers are periodically removed by wet or dry type evacuation methods.
The supporting structure of the Electrostatic precipitators is designed for the vertical load exerted mainly by the collecting electrodes and the weight of the collected ash in the hopper including the horizontal loads of wind and earthquake.
The bearing level of the supporting structure (i.e.) the junction between the rectangular shaped box, housing the collecting electrodes and emitting electrodes at the top and the inverted pyramidal hopper at the bottom, is decided by the hopper size which is depended on the ash-storage capacity and the valley angle. Valley angle of the hopper is the minimum slope required in the side walls of the hopper for an easy removal of the collected ash from the hopper.
The bearing level of the hopper bottom is decided by the type of ash evacuation methods namely wet or dry type.
The supporting structure of the Electrostatic precipitator is a structure of columns, beams and bracings erected from the foundation level to the bearing level.
The supporting structure columns are provided at all four corners of the pyramidal hopper, so that the vertical loads from the hoppers storing the ash, is transferred to the columns directly.

The general layout of a power plant consists of a Boiler, an Electro Static Precipitator (ESP), a plurality of Induced Draft fans (ID fans) and a Chimney located in series.
Normally, a road is provided in between the ESP and the ID Fan to cater for removal and transportation of the impeller of the ID fan for maintenance. The road is configured between the last row of the ESP supporting columns and the first row of the ID Fan handling the structure. The fan handling columns is provided with a monorail for handling of the ID fan shaft/impeller for maintenance.
The funnel of the ESP is normally located above the road and at a height more than the normal handling height of the fan impeller.
As stated earlier, any new ESP designed to correspond the new emission norms results into a bigger size ESP and always becomes longer and taller than the existing ESP which is to be replaced.
In the prior art layout, the new ESP has to be fitted in a place where the prior art ESP was located.
Since the new ESP is longer than the prior art ESP and at times the last column of the ESP comes in the road, the transportation of the ID fan impeller becomes a problem.
This invention tries to solve the said disadvantages of the prior art.

OBJECTS OF THE INVENTION:
It is therefore an object of the invention to propose an improved supporting device converting existing Electrostatic precipitators complaint to statutory level of reduced emission of dust particles.
Another object of the invention is to propose an improved supporting device converting existing Electrostatic precipitators complaint to statutory level of reduced emission of dust particles, in which an unobstructed road between the ESP and ID fan is provided.
A still another object of the invention is to propose an improved supporting device converting existing Electrostatic precipitators complaint to statutory level of reduced emission of dust particles, in which a cantilever bracket is provided from the bearing to the last shifted column to provide the unobstructed road.
Yet another object of the invention is to propose an improved supporting device converting existing Electrostatic precipitators complaint to statutory level of reduced emission of dust particles, which enables the bearings of the ESP in the cantilever to transfer the load from the ESP to the supporting device.
Another object of the invention is to propose an improved supporting device converting existing Electrostatic precipitators complaint to statutory level of reduced emission of dust particles, in which bracings are provided in the longitudinal axis to transfer the load from the cantilever to the foundation smoothly.

A still another object of the invention is to propose an improved supporting device converting existing Electrostatic precipitators complaint to statutory level of reduced emission of dust particles, in which transverse bracings are provided to transfer the major wind and earthquake loads from the beams level to the foundation.
A further object of the invention is to propose an improved supporting device converting existing Electrostatic precipitators complaint to statutory level of reduced emission of dust particles, wherein the transverse bracings are provided without interference with the hoppers of ESP.
A still further object of the invention in to propose an improved supporting device converting existing Electrostatic precipitators complaint to statutory level of reduced emission of dust particles, in which the horizontal member connecting the top of shifted ESP columns across the gas flow is removed to prevent piercing of the tie beams through the hopper.
Yet further object of the invention is to an improved supporting device converting existing Electrostatic precipitators complaint to statutory level of reduced emission of dust particles, in which a heavy beam at the middle height of the cross bracings in the traverse direction is provided to safely transfer the moments to the columns and hence to the foundations.
SUMMARY OF THE INVENTION:
The supporting device of the ESP is provided from the bearing level of the ESP to the finish floor (Level 0.0) of a thermal power plant.

The supported device consists of a plurality of columns to take the vertical load and bracings along the longitudinal and transverse axes to take care of the horizontal loads. These columns and bracings transfer the loads from the bearing to the foundations.
The columns are normally provided at every corner of the hopper which usually consists of an inverted pyramid made of steel plates.
The bracing are provided connecting the column top and the foundation top.
Normally the last column of the ESP cannot be shifted from the original location since transverse bracing interfere with the hopper of the ESP due to shifting of the last column.
Because of these reasons, the columns (last) row are never shifted from the original location of ESPs.
But an innovative bracing system proposed in this invention takes care of this aspect and does not interfere with the hoppers.
The shifting of the column necessitates a cantilever bracket to be introduced for transfer of the load from the bearing of the last column to the shifted column.
The horizontal member which is normally provided at the top of columns to interconnect the columns and transfer horizontal load is entirely removed in the transverse direction at the top of the shifted column in the present invention.

This invention facilitates the provision of retrofit ESPs to be accommodated in the available space between the last column of the boiler and I.D fan thereby gaining precious space of the road width available in the layout.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING:
Figure-1 shows sectional elevations and plan view of the existing bracing system of the ESP.
Figure-2 shows sectional elevations and plan view of the modified bracing system required for the shifting of last column of ESP towards boiler to avoid interference of the column with the road between ESP and ID fan according to the invention.
DETAILED DESCRIPTION OF THE INVENTION:
As shown in Figure-2, the supporting device for the ESP is provided with a shifted last column to avoid fouling of the last column (8) in the road.
The shifting of the last column (8) is done for necessary distance to avoid fouling of the last column with the roads between the last location of the last column of the ESP and the ID fan.
A cantilever bracket (1) is provided from the bearing level at old column location to near mid-height of the shifted last column (8).

The longitudinal bracings (2) of the supporting device of ESP are designed in such a way that loads from the bearing (9) on the cantilever is smoothly transferred to the foundation.
The transverse bracing system in designed and given a slope such a way that it does not interfere with the hoppers of the ESP.
The top horizontal member (7) interconnecting the ESP columns in the transverse direction are eliminated, and the modified bracing is designed for all the horizontal force transfer to the foundations safely.
The top horizontal member (3) of the cantilevered bracket is designed for transferring their horizontal forces from the bearing to column top by beam action.
The transverse bracing is provided with a central horizontal member (8) in the middle to transfer the load from the top inclined member to the foundation.
The cantilever top member supporting the bearings are connected by a horizontal member (5) in the transverse direction through which the horizontal load is transferred to the column top via the cantilever top member (3).
To reduce the member size, small brackets (4) are provided to the horizontal member in the transverse direction at the bearing (9) level.
The cantilever bracketed arrangement is also provided in the boiler side column to make the supporting device symmetrical.

WE CLAIM:
1) An improved supporting device converting existing Electrostatic precipitators complaint to statutory level of reduced emission of dust particles bracketed cantilever arrangement (1) whereby the last column of the ESP is shifted towards boiler; a bracing in the longitudinal direction (2) which smoothly transfers the vertical load from the bracketed cantilever (1) arrangement to the foundation of the ESP; a horizontal member (3) connecting the top of the cantilevered bracket which supports the bearings (9) of the ESP columns; a transverse bracing having top inclined members (6) with a slope parallel to the hopper side slope so that the inclined member does not interfere with the hopper and a horizontal member (8) located at the middle of the transverse bracing inter connecting the columns for transferring the horizontal forces to the foundation by beam action.
2) The supporting device as claimed in claim 1, comprising tie members (4) connected to a horizontal transverse member (5) at the top of the cantilevered bracket (1).
3) The supporting device as claimed in any of the preceding claims, wherein the columns and bracings are made up of built up rolled steel channel sections.